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16.2. Using PTP

In order to use PTP, the kernel network driver for the intended interface has to support either software or hardware time stamping capabilities.

16.2.1. Checking for Driver and Hardware Support

In addition to hardware time stamping support being present in the driver, the NIC must also be capable of supporting this functionality in the physical hardware. The best way to verify the time stamping capabilities of a particular driver and NIC is to use the ethtool utility to query the interface as follows:
~]# ethtool -T em3
Time stamping parameters for em3:
Capabilities:
        hardware-transmit     (SOF_TIMESTAMPING_TX_HARDWARE)
        software-transmit     (SOF_TIMESTAMPING_TX_SOFTWARE)
        hardware-receive      (SOF_TIMESTAMPING_RX_HARDWARE)
        software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
        software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
        hardware-raw-clock    (SOF_TIMESTAMPING_RAW_HARDWARE)
PTP Hardware Clock: 0
Hardware Transmit Timestamp Modes:
        off                   (HWTSTAMP_TX_OFF)
        on                    (HWTSTAMP_TX_ON)
Hardware Receive Filter Modes:
        none                  (HWTSTAMP_FILTER_NONE)
        all                   (HWTSTAMP_FILTER_ALL)
Where em3 is the interface you want to check.
For software time stamping support, the parameters list should include:
  • SOF_TIMESTAMPING_SOFTWARE
  • SOF_TIMESTAMPING_TX_SOFTWARE
  • SOF_TIMESTAMPING_RX_SOFTWARE
For hardware time stamping support, the parameters list should include:
  • SOF_TIMESTAMPING_RAW_HARDWARE
  • SOF_TIMESTAMPING_TX_HARDWARE
  • SOF_TIMESTAMPING_RX_HARDWARE